This invention relates in general to vehicle transmissions and in particular to an improved structure for facilitating the use of an electronic controller with a number of different mechanical transmission structures to provide a partially or fully automated manual transmission.
In most vehicles, a transmission is provided in the drive train between the engine and the driven wheels. As is well known, the transmission includes a case containing an input shaft, an output shaft, and a plurality of meshing gears. Means are provided for connecting selected ones of the meshing gears between the input shaft and the output shaft to provide a desired speed reduction gear ratio therebetween. The meshing gears contained within the transmission case are of varying size so as to provide a plurality of such gear ratios. By appropriately shifting among these various gear ratios, acceleration and deceleration of the vehicle can be accomplished in a smooth and efficient manner.
The shifting of the transmission among the available gear ratios is frequently accomplished manually, wherein the selection and engagement of a specific gear ratio is performed in response to some physical exertion by the vehicle driver. Most commonly, the driver grasps and physically moves an upper portion of an elongated shift lever. In response thereto, a lower portion of the shift lever engages and moves one of a plurality of shift rails provided within the transmission. Movement of the selected shift rail causes certain ones of the meshing gears to be connected between the input shaft and the output shaft so as to provide the desired gear ratio therebetween. Manually shifted transmissions are desirable because they are relatively simple, inexpensive, and lightweight in structure and operation. Because of this, the majority of medium and heavy duty truck transmissions in common use today are manually shifted transmissions.
In order to improve the convenience of use of manually shifted transmissions, various structures have been proposed for partially or fully automating the shifting thereof. In a partially automated manual transmission, the driver-manipulated shift lever engages and moves certain ones of the shift rails, while an automatic shifting mechanism (which may be hydraulically or pneumatically actuated) engages and moves the remaining shift rails. For example, the lower gear ratios of a partially automated manual transmission may be manually selected and engaged by the vehicle driver using the shift lever, while the higher gear ratios are automatically selected and engaged by the automatic shifting mechanism. In a fully automated manual transmission, the driver-operated shift lever is usually replaced by the automatic shifting mechanism. The automatic shifting mechanism functions to shift all of the shift rails within the transmission throughout all of the available gear ratios. A partially automated manual transmission is advantageous, particularly in long haul and similar trucking applications, because it is lower in cost than a comparable fully automated manual transmission, yet offers automatic shifting in the higher gear ratios where the majority of shifting between gears normally occurs.
In all types of transmissions, decisions must be made as to when to shift the transmission out of a current gear ratio and into a new gear ratio. For a given transmission structure, these shifting decisions (referred to in the aggregate as the shifting strategy for the transmission) are typically based upon a number of operating conditions for the vehicle and the transmission, such as engine speed, vehicle speed, current gear ratio, throttle position, and the like. In manually shifted transmissions, the shifting decisions are made by the driver of the vehicle based upon experience. In both partially and fully automated transmissions, however, the shifting decisions are made by an electronic controller. To accomplish this, the electronic controller includes a plurality of sensors which generate electrical signals which are representative of a number of the predetermined operating conditions of the vehicle. These electrical signals are fed to the electronic controller which, in turn, is programmed to shift the transmission out of a current gear ratio and into a new gear ratio when certain predetermined operating conditions have been sensed.
In order to properly decide when a shift should occur in response to these sensed operating conditions, the electronic controller should be programmed with information regarding the specific structure of the transmission with which it is being used. Primarily, this information includes the quantity of gear ratios which are contained within the transmission and the specific magnitudes of such gear ratios. This basic transmission structure information, together with the sensed operating conditions discussed above, will determine the most efficient shifting strategy for that particular transmission structure. As is well known, transmissions vary widely in structure in order to accommodate vehicles of differing size, weight, and intended use. For example, the quantity of gear ratios which are contained within the transmission may vary from as low as three or four gear ratios (such as for a small automobile) to as high as sixteen or eighteen gear ratios (such as for a large truck). Additionally, the magnitudes of the specific gear ratios which are available for use will vary, even among transmissions having the same quantity of gear ratios. For example, the magnitude of the highest gear ratio available in some ten-speed transmissions is a 1:1.00 direct drive gear ratio, wherein the rotational speed of the output shaft of the transmission is equal to the rotational speed of the input shaft. The magnitude of the highest gear ratio available in other ten-speed transmissions is a 1:0.75 over drive gear ratio, wherein the rotational speed of the output shaft of the transmission is greater than the rotational speed of the input shaft. Obviously, therefore, differing transmission structures will have differing shifting strategies for optimum operation.
Ideally, each electronic controller would be programmed with the specific information which relates to the particular transmission structure with which it is intended to be used. In this instance, the electronic controller would be programmed within only a single shifting strategy which relates to that particular transmission structure. As a practical matter, however, such an arrangement would be rather inefficient, inasmuch as it would require that each electronic controller be individually programmed with a specific shifting strategy when it is manufactured and assembled with a particular underlying transmission structure. One possible simplification of this procedure would be to initially store a plurality of shifting strategies (relating to a plurality of different transmission structures) in all of the electronic controllers, and then to manually identify to the electronic controller which particular transmission strategy is to be used. Based upon this manual input, the electronic controller would select the desired one of the plurality of shifting strategies for use. Unfortunately, this procedure still somewhat inefficient, inasmuch as it requires an individual to manually identify the transmission structure which is being used and to properly program the electronic controller to identify that transmission structure. Also, if the electronic controller is subsequently removed from a first transmission structure and installed on a second different transmission structure, it requires re-programming of the electronic controller for proper operation with new information. Thus, it would be desirable to provide an improved structure for an electronic controller which can automatically identify the structure of the transmission which with it is being used and program itself to use pre-programmed information regarding that transmission structure to efficiently effect automatic shifting of the transmission in response to sensed operating conditions.